Sinking methods and costs for a small vertical shaft with steel supports :Keystone mine, Crested Butte, Colorado

Author:	Bolmer, R. L.
Year:	1962
Document Type:	USBI
Issuing Agency:	U.S. Dept. of the Interior, Bureau of Mines,
SUDOC:	I 28.27:8086
Series:	Information circular / United States Department of the Interior, Bureau of Mines ;
Report Number:	8086
Subjects:	Lead mines and mining--Colorado--Gunnison County
	Shaft sinking--Costs
	Shaft sinking
Link:	https://hdl.handle.net/2027/mdp.39015078456467